When examining a target lesion such as a blood vessel, a Vessel, and the like inside a body lumen, an ultrasound catheter which transmits and receives ultrasounds at the target lesion is used. The ultrasound catheter includes an imaging core that comprises a transducer unit which transmits and receives ultrasounds and a drive shaft which rotates the transducer unit, and a sheath that has the imaging core built in and is inserted into a lumen. The imaging core can move inside the sheath in an axial direction.
Generally, when using the ultrasound catheter, an introducer sheath for providing access to the inside of the lumen is indwelled, and a guiding catheter is inserted into the lumen via the introducer sheath. Thereafter, a guide wire is inserted through the guiding catheter until the guide wire reaches a target place, and the ultrasound catheter is inserted along the guide wire to a site deeper than the target lesion. Then, from a state where the imaging core is disposed inside the sheath on a distal side, only the imaging core is caused to move backward and to pass through the target lesion while leaving the sheath behind. Since the transducer unit moves from the deep site while passing through the target lesion by moving only the imaging core backward, it is possible to observe ultrasound images which are continuously acquired through the front and the rear of the target lesion, and to generate three-dimensional data of shapes of a blood vessel, a Vessel, or the like.
In order to facilitate the imaging core to move in the axial direction inside the sheath, for example, the ultrasound catheter disclosed in International Application Publication No. WO 1999/015078 comprises a nested structure for extending and contracting in the axial direction provided in the sheath on a proximal side, the imaging core inside the sheath is caused to move in the axial direction with respect to the sheath by varying the overall length of a catheter main body.
Then, in the ultrasound catheter disclosed in International Application Publication No. WO 1999/015078, a connection portion which is connectable and disconnectable is provided between the sheath and the nested structure, and the imaging core can be pulled out of the catheter main body in accordance with a situation.